Process for building up an edge of a machine component, and machine component remanufacturing strategy

ABSTRACT

A process for building up a leading edge of a machine component such as a leading edge of a turbine blade for a turbocharger includes forming a molten pool along the edge of the machine component, feeding a filler material in a solid state into the molten pool and melting the filler material via heat transfer between the molten pool and the filler material. A solid layer may be formed along the leading edge by cooling the molten pool. The process is applicable to remanufacturing damaged machine components having a plurality of blades with relatively thin leading edges.

TECHNICAL FIELD

The present disclosure relates generally to strategies for depositing alayer of filler material along a thin edge of a machine component, andrelates more particularly to melting filler material via heat transferwith a molten pool formed along a thin edge of a machine component.

BACKGROUND

Many machine components are used in relatively demanding operatingenvironments which can lead to damage or wear over time. The relativelyhigh temperatures and pressures associated with many turbineapplications are one example of a relatively demanding operatingenvironment. Turbine wheels used in connection with turbochargerscommonly develop blade damage after a certain period of service,depending upon the particular service conditions.

When an internal combustion engine is started or stopped, many of itscomponents tend to heat or cool, respectively, relatively rapidly.Differing rates of expansion or contraction among components of theinternal combustion engine can generate many relatively small particleswhich dislodge from the components. In an exhaust system, such particlesmay become airborne and impact blades of a turbocharger's turbine wheelrelatively hard, adding to the already demanding nature of theenvironment. Micro-cracks, pits, chips and other forms of blade damagecan occur due to impacts with particles, or for other reasons in aconventional turbocharger. When an associated internal combustion engineor certain of its components are removed from service, such as forremanufacturing, damaged turbine wheels are typically scrapped. Sinceturbine wheels are relatively highly machined and precisely designedcomponents, the economic downside to wholesale scrapping of turbinewheels will be readily apparent.

A number of strategies for repairing bladed components, such as turbinevanes used in gas turbine engines, have been proposed over the years.United States Patent Application Publication No. 2006/0049153 to Cahoonet al. (“Cahoon”) is directed to a dual feed laser welding system whichis purportedly applicable to gas turbine engine components for automatedwelding repairs. Cahoon proposes feeding a filler material through awire feeder, then melting the filler material via a laser and permittingthe melted filler material to be deposited on a component to berepaired. While Cahoon may be applicable in certain instances, thestrategy is not without drawbacks. Positioning the filler material wirewithin a laser beam, elevated from the component to be repaired, tendsto reflect a certain amount of the laser light by way of the typicallyshiny outer surface of the wire. In addition, the melted filler materialis apparently dropped or spattered onto the component to be repaired,which would tend to waste material and reduce the overall precision,quality and consistency of the welding process. Various proposals forpowder spray welding and other strategies suffer from similar drawbackswith regard to wasting material and consuming laser energy.

The present disclosure is directed to one or more of the problems orshortcomings set forth above.

SUMMARY

A process for building up an edge of a machine component includes thesteps of forming a molten pool of a first material along the edge of themachine component by melting the machine component via a laser, andfeeding a second material in a solid state into the molten pool. Theprocess further includes the steps of melting the second material withinthe molten pool via heat transfer with the molten pool, and forming asolid layer including a mixture of the first material and the secondmaterial along the edge of the machine component by cooling the moltenpool.

In another aspect, a method of remanufacturing a machine componenthaving a leading edge includes a step of receiving a machine componentremoved from service having a leading edge which defines a leading edgecontour different from a specified contour. The method further includesthe steps of returning the leading edge contour to the specified contourat least in part via the steps of forming a molten pool of a firstmaterial along the leading edge of the machine component by melting themachine component via a laser and feeding a second material comprising afiller material in a solid state into the molten pool. The step ofreturning the leading edge contour to the specified contour furtherincludes a step of melting the second material within the molten poolvia heat transfer with the molten pool and forming a solid layerincluding a mixture of the first material and the second material alongthe leading edge by cooling the molten pool.

In still another aspect, a machine component is remanufactured accordingto a process which includes the step of receiving a machine componenthaving a leading edge which defines a leading edge contour differentfrom a specified contour. The process further includes a step ofreturning the leading edge contour to the specified contour at least inpart via the steps of forming a molten pool of a first material alongthe leading edge of the machine component by melting the machinecomponent via a laser, feeding a second material including a fillermaterial in a solid state into the molten pool, and melting the secondmaterial within the molten pool via heat transfer with the molten pool.The step of returning the leading edge contour to the specified contourfurther includes a step of forming a solid layer including a mixture ofthe first material and the second material along the leading edge bycooling the molten pool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a machine component removed fromservice, according to one embodiment;

FIG. 2 is a diagrammatic view of a machine component at aremanufacturing stage, according to one embodiment;

FIG. 3 a is a diagrammatic view of a portion of a machine component atanother remanufacturing stage, according to one embodiment;

FIG. 3 b is a diagrammatic view of a machine component at theremanufacturing stage of FIG. 3 a, in a different perspective;

FIG. 4 is a sectioned diagrammatic view of a machine component, in twosection planes, at another remanufacturing stage, according to oneembodiment; and

FIG. 5 is a diagrammatic view of a remanufactured machine component,according to one embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a machine component 10 removed fromservice. In the illustrated embodiment, machine component 10 is arotatable machine component having a plurality of radially arrangedblades 12, 112. Machine component 10 further includes a body 14 coupledwith a shaft 16. Machine component 10 is illustrated in the context of aturbine wheel for a conventional turbocharger, however, it should beappreciated that the present disclosure is not limited to turbinewheels. In other embodiments, other rotatable machine components, bladedor non-bladed, and even non-rotatable machine components might beadvantageously processed according to the teachings set forth herein. Inthe illustrated embodiment, machine component 10 (hereinafter turbinewheel 10) has a plurality of damaged blades 12 and a plurality ofsubstantially undamaged blades 112. In some instances, when a turbinewheel such as turbine wheel 10 is removed from service all of its bladesmay be damaged, or only a small number of the blades may be damaged. Inany event, damaged blades 12 may have a leading edge 18 which defines aleading edge contour different from a specified contour. The differencebetween the leading edge contour and a specified contour may result fromdamage to leading edge 18, such as the presence of chips 20 or othermalformations resulting from operation of turbine wheel 10 when inservice in a turbocharger. Undamaged blades 112 include a substantiallyundamaged leading edge 118 which approximates the specified leading edgecontour described herein. The differences between damaged leading edges18 and undamaged leading edges 118 will be readily apparent in FIG. 1.

The present disclosure provides a strategy for building up an edge on amachine component, such as turbine wheel 10, whereby a leading edgecontour which differs from a specified contour may be returned to thespecified contour. To this end, when turbine wheel 10 is received afterremoving from service in a turbocharger, etc., it may be remanufacturedaccording to processes described hereinbelow. Turning to FIG. 2, thereis shown turbine wheel 10 at a remanufacturing stage according to oneembodiment. Remanufacturing of turbine wheel 10 may begin by inspectingturbine wheel 10 for major damage, or other conditions which mightrender it unsuitable for ever returning to service. For instance, ifshaft 16 were bent or cracked, turbine wheel 10 might be considered notamenable to remanufacturing and therefore scrapped. Likewise, damage toone or more of blades 12 could in some instances be so severe thatattempted remanufacturing of turbine wheel 10 would not be consideredworthwhile. In any event, following an initial inspection stage, turbinewheel 10 might be cleaned and prepared for further processing. Onceappropriately prepared, turbine wheel 10 may be processed via a firstmachining apparatus 100 to remove material 22 of each damaged turbineblade 12. In FIG. 2, a line L represents a demarcation between material22 to be removed, and material 25 which is to remain. Machiningapparatus 100 may include a base 102 and a rotatable tool 104, such as arotary grinder, which is used to grind or otherwise remove material 22from each of damaged turbine blades 12. It will be noted in the FIG. 2illustration that material corresponding to a portion of each one of aplurality of blades 12 has been removed, and machining apparatus 100 isengaged with one of blades 12. Machining damaged blades 12 via machiningapparatus 100 may be undertaken to prepare each leading edge 18 forfurther processing by providing a relatively uniform, level andotherwise clean leading edge 18 on each of the damaged blades 12.

Turning now to FIG. 3 a, there is shown turbine wheel 10 at anotherremanufacturing stage. At the remanufacturing stage depicted in FIG. 3a, a laser apparatus 200 may be positioned in proximity to turbine wheel10 and used to deposit material along leading edge 18 to build upleading edge 18, thereby returning a leading edge contour defined byleading edge 18 to the specified contour, as described herein. Laserapparatus 200 may include a housing 202 having an emitter 204 coupledtherewith which is configured to emit a laser beam 206 and locate a beamspot 208 of beam 206 on leading edge 18. In one embodiment, emitter 204may comprise a diode laser emitter and beam 206 may be a flat beamhaving a rectangular configuration, with a corresponding rectangularbeam spot 208, which is oriented longitudinally along leading edge 18.In other words, a longer dimension of beam spot 208 may be oriented suchthat it is generally aligned with a length dimension of leading edge 18,between a first end 24 and a second end 26 of leading edge 18. Laserapparatus 200 may further include a support arm 210 having a wirefeeding apparatus 212 mounted thereon. Wire feeding apparatus 212 mayinclude a housing 214 and a feeder 216 which is a pull-type feedermounted therein. Feeder 216 may be configured to feed a wire 220 from awire spool (not shown). Wire 220 may be guided via wire guide 218 in adesired orientation to a desired location along leading edge 18.

Many earlier laser deposition processes, such as Cahoon described above,utilized strategies for feeding of filler material and laserconfigurations having a variety of shortcomings, at least when appliedto building up thin edges of machine components. The present disclosureovercomes problems associated with such earlier designs. In oneembodiment, laser apparatus 200 may be used to form a solid layer 28along leading edge 18 to build up leading edge 18. Forming solid layer28 may take place by forming a plurality of molten pools 30 of a firstmaterial along leading edge 18 by melting turbine wheel 10 via laserbeam 206. Laser apparatus 200 may be moved relative to turbine wheel 10such that beam spot 208 moves longitudinally along leading edge 18 fromfirst end 24 of blade 12 toward second end 26 of blade 12.Alternatively, turbine wheel 10 might be moved relative to laserapparatus 200. As beam spot 208 traverses leading edge 18, it may meltmachine component 10 to form a plurality of overlapping molten pools 30,which successively solidify as they cool. While moving beam spot 208 asdescribed, a second material which includes a filler material such aswire 220 may be fed in a solid state into the molten pool presentlyformed via beam 206. As wire 220 is fed into molten pool 30, wire 220may melt via heat transfer between molten pool 30 and the material ofwire 220. Cooling of each molten pool may result therefore in depositionof a solid layer 28. Solid 28 may thus include a mixture of the firstmaterial, material of turbine wheel 10, and the second material,material of wire 220. Where a layer of material has already beendeposited along leading edge 18, the “first” material may includepreviously deposited filler material. In this general manner, solidlayer 28 may be deposited along an entirety of leading edge 18 fromfirst end 24 to second end 26. It should be appreciated that melting ofmaterial of turbine wheel 10 along leading edge 18 may be such that onlya single molten pool 30 exists at any one time, or such that multiplepools of cooling yet still molten material exist at once.

As mentioned above, wire 220 may be melted via heat transfer betweenmolten pool 30 and the material of wire 220. It should be understoodthat the present description of melting material of wire 220 via heattransfer with molten pool 30 differs from earlier strategies where afiller material was melted by directly applying a laser beam to thefiller material. In one embodiment, wire 220 may be fed into molten pool30 in a region of molten pool 30 which is not within beam spot 208. Inthe embodiment shown in FIG. 3 a, wire 220 is fed into molten pool 30ahead of beam spot 208 as beam spot 208 traverses leading edge 18. Inother embodiments, wire 220 might be fed into a different portion ofmolten pool 30 than that which is shown. It has been discovered thatusing a rectangular beam spot provides a relatively longer molten pool,resulting in relatively greater time for mixing of the material of wire220 with material of turbine wheel 10 than would be available withanother beam spot shape, such as a circular shape. This has been foundto result in a relatively greater uniformity of solid layer 28.Depending upon the relative width of blade 12, beam spot 208 may beoscillated back and forth across its width to enhance melting and/ormixing of the respective materials, or for other purposes.

Turning to FIG. 3 b, there is shown laser apparatus 200 and turbinewheel 10 approximately at the same stage depicted in FIG. 3 a, but froma different perspective. As shown in FIG. 3 b, wire 220 may be fed intomolten pool 30 ahead of beam spot 208. It may also be noted that wire220 may be fed into molten pool 30 such that wire 220 does not contact abottom 31 of molten pool 30. Once solid layer 28 has been depositedalong an entirety of leading edge 18 or a desired portion of leadingedge 18 less than its entirety, machine component 10 or laser apparatus200 may be reoriented for deposition of an additional solid layer on topof solid layer 28. Depending upon the extent to which a height of blade12 is to be built up, many layers may be successively deposited one ontop of the other along leading edge 18 until leading edge 18 is built upto a desired height. An inert gas shield may be used in the vicinity ofbeam spot 208 to avoid forming of oxides on or around molten pool 30. Itmay also be desirable to flood leading edge 18 with inert gas duringforming each layer, or perform the welding operation in an inert gaschamber. Leading edge 18 may then be finish machined, etc., to restorethe leading edge contour defined by leading edge 18 to the specifiedcontour.

Turning now to FIG. 4, there is shown a sectioned view taken in twosection planes through a portion of blade 12 after processing via theremanufacturing stages depicted in FIGS. 2, 3 a and 3 b. It will benoted that a plurality of solid layers 28 have been formed on leadingedge 18. It may further be noted that new material 23 which includessolid layers 28 is positioned on one side of line L, whereas oldmaterial 25 is positioned on an opposite side of line L. In theembodiment shown, old material 25 includes material between a base edge36 of blade 12 and line L, whereas new material 23 includes materialbetween line L and a leading edge 118 of blade 12 which has beenreturned to the specified contour. In the embodiment shown, solid layers28 which are relatively further from base edge 36 have a first widthwhich is relatively lesser than a width of solid layers 28 which arerelatively closer to base edge 36. In one embodiment, an average widthof each of layers 28 may be about 1 mm or less, and an average thicknessof layers 28 may be about 1 mm or less. Another machining apparatus 300,having a base 302 and a tool 304 such as a rotary grinder, is shown asit might appear having just completed forming a ground surface 38 onblade 12 to finish machine blade 12 and return the leading edge contourto the specified leading edge contour.

Turning now to FIG. 5, there is shown a turbocharger 40 having turbinewheel 10 coupled therewith. Turbocharger 40 includes a turbine housing42, a compressor housing 44 having a compressor wheel 46 therein and ashaft 48 connecting compressor wheel 46 with turbine wheel 10. As shownin FIG. 5, turbine wheel 10 has thus been reassembled with othercomponents of a turbocharger in preparation for returning to service.

INDUSTRIAL APPLICABILITY

Many different techniques for repair of all manner of machine componentsare known, including a variety of laser deposition techniques suitablefor building up material along an edge. Known strategies suffer fromdrawbacks, however, such as spattering and material waste, as describedabove. The present disclosure provides a new technique whichadvantageously addresses these and other concerns. In building up anedge of a machine component according to the present disclosure,materials which are easily targeted to a location along leading edge 18,relatively inexpensive and relatively easy to melt may be used as thefiller material. Moreover, since wire 220 is not exposed in a moltenstate to air prior to melting in pool 30, oxidation and evaporation maybe reduced, as well as absorption of gases by molten material. In thepresent disclosure, essentially no molten material will be deposited onleading edge 18 outside of molten pool 30, enhancing fusion anduniformity and minimizing defects. Further still, since melting wire 220via enthalpy of molten pool 30 is relatively highly efficient losses ofbeam energy such as what may occur where a wire is placed in a path of alaser are reduced. Relatively high wire feeding speeds of up to 30-40inches per minute may therefore be used.

The present description is for illustrative purposes only, and shouldnot be construed to narrow the breadth of the present disclosure in anyway. Thus, those skilled in the art will appreciate that variousmodifications might be made to the presently disclosed embodimentswithout departing from the full and fair scope and spirit of the presentdisclosure. For instance, while repairing damaged turbine blades is oneapplication of the teachings set forth herein, the present disclosure isnot thereby limited. Many machine systems have thin-walled componentshaving edges, such as flanges, susceptible to damage which could readilybe repaired according to the present disclosure. Moreover, the presentdisclosure may be applied outside the context of repair andremanufacturing, for instance in making new parts having thin edges andthe like which are to be built up to specified heights, contours, etc.Furthermore, while it is contemplated that feeding wire 220 at arelatively constant feed rate and moving laser apparatus 200 at arelatively constant speed relative to leading edge 18 will be apractical implementation strategy for forming a smooth, uniformly thicklayer 25, alternatives are contemplated. In other embodiments, wire feedrate and/or the relative speed with which beam spot 208 is moved alongleading edge 208 might be varied to vary characteristics of solid layer28, such as uniformity, thickness, etc., for various applications. Otheraspects, features and advantages will be apparent upon an examination ofthe attached drawings and appended claims.

1. A process for building up an edge of a machine component comprisingthe steps of: forming a molten pool of a first material along the edgeof the machine component by melting the machine component via a laser;feeding a second material comprising a filler material in a solid stateinto the molten pool; melting the second material within the molten poolvia heat transfer with the molten pool; and forming a solid layercomprising a mixture of the first material and the second material alongthe edge of the machine component by cooling the molten pool.
 2. Theprocess of claim 1 wherein the step of forming a molten pool comprises astep of applying a beam of a diode laser to the edge of the machinecomponent, and wherein the step of feeding a second material furthercomprises feeding a wire into the molten pool.
 3. The process of claim 2wherein the step of applying a beam of a diode laser comprises locatinga beam spot of the beam on the edge of the machine component, andwherein the step of feeding a second material comprises feeding the wireinto a portion of the molten pool which is not within the beam spot. 4.The process of claim 3 wherein the step of feeding a second materialfurther comprises feeding the wire into the molten pool withoutcontacting a bottom of the molten pool.
 5. The process of claim 3wherein the step of applying a beam further comprises applying a flatbeam having a rectangular beam spot and orienting the rectangular beamspot longitudinally along the edge of the machine component, the processfurther comprising a step of moving the beam spot longitudinallyrelative to the edge of the machine component during the forming stepand during the feeding step.
 6. The process of claim 5 wherein the stepof feeding the second material comprises feeding the wire into themolten pool ahead of the beam spot during moving the beam spot.
 7. Theprocess of claim 7 wherein the step of forming a solid layer comprisesbuilding up the edge of the machine component via a first solid layer,the process further comprising a step of further building up the edgevia a plurality of additional solid layers.
 8. The process of claim 7comprising a process for building up a leading edge of a turbine blade,wherein the step of forming a solid layer comprises forming a firstsolid layer having a first width and wherein the step of furtherbuilding up the edge includes forming a second solid layer having asecond, relatively lesser width.
 9. The process of claim 8 furthercomprising a step of oscillating the beam spot back and forth across awidth of the edge of the machine component during forming a first solidlayer.
 10. A method of remanufacturing a machine component having aleading edge comprising the steps of: receiving a machine componentremoved from service having a leading edge which defines a leading edgecontour different from a specified contour; and returning the leadingedge contour to the specified contour at least in part via the steps offorming a molten pool of a first material along the leading edge of themachine component by melting the machine component via a laser, feedinga second material comprising a filler material in a solid state into themolten pool, melting the second material within the molten pool via heattransfer with the molten pool and forming a solid layer comprising amixture of the first material and the second material along the leadingedge by cooling the molten pool.
 11. The method of claim 10 wherein themachine component comprises a rotatable element having a plurality ofblades, and wherein the receiving step comprises receiving a rotatableelement having at least one damaged blade which defines the leading edgecontour different from the specified contour.
 12. The method of claim 11further comprising a step of preparing the leading edge prior to thestep of returning the leading edge contour to a specified contour,including removing damaged material of the at least one damaged blade.13. The method of claim 12 wherein the step of forming a molten poolcomprises applying a flat beam of a diode laser to the leading edge ofthe machine component, including locating a rectangular beam spot of theflat beam on the leading edge of the machine component, and wherein thestep of melting the second material within the molten pool comprisesfeeding a wire into a portion of the molten pool which is not within therectangular beam spot.
 14. The method of claim 13 wherein the step offorming a solid layer comprises forming a first solid layer and the stepof returning the leading edge contour to the specified contour comprisesbuilding up the leading edge via the first solid layer, the step ofreturning the leading edge contour to the specified contour furthercomprising building up the leading edge via forming a plurality ofadditional solid layers along the leading edge.
 15. The method of claim14 wherein the method comprises a method of remanufacturing aturbocharger, and further comprising the steps of returning a pluralityof leading edges of a plurality of damaged blades of a damaged turbinewheel for the turbocharger to the specified contour, then reassemblingthe turbine wheel with a turbocharger housing.
 16. A machine componentremanufactured according to a process comprising the steps of: receivinga machine component having a leading edge which defines a leading edgecontour different from a specified contour; and returning the leadingedge contour to the specified contour at least in part via the steps offorming a molten pool of a first material along the leading edge of themachine component by melting the machine component via a laser, feedinga second material comprising a filler material in a solid state into themolten pool, melting the second material within the molten pool via heattransfer with the molten pool and forming a solid layer comprising amixture of the first material and the second material along the leadingedge by cooling the molten pool.
 17. The machine component of claim 16wherein the step of forming a solid layer comprises forming a firstsolid layer and the step of returning the leading edge contour to thespecified contour comprises building up the leading edge via the firstsolid layer, the step of returning the leading edge contour to thespecified contour further comprising building up the leading edge viaforming a plurality of additional solid layers along the leading edge.18. The machine component of claim 17 comprising a turbine wheel for aturbocharger having a plurality of turbine blades.
 19. The machinecomponent of claim 18 wherein the receiving step further comprisesreceiving a turbine wheel having a plurality of damaged turbine bladeseach defining a leading edge contour different from the specifiedcontour, the process further comprising a step of returning the leadingedge contour of each one of the damaged turbine blades to the specifiedcontour.